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प्रश्न
How many different numbers of six digits each can be formed from the digits 4, 5, 6, 7, 8, 9 when repetition of digits is not allowed?
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उत्तर
Number of ways of filling the first digit = 6
Number of ways of filling the second digit = 5
(as repetition is not allowed)
Number of ways of filling the third digit = 4
Number of ways of filling the fourth digit =3
Number of ways of filling the fifth digit = 2
Number of ways of filling the sixth digit = 1
Total numbers = `6xx5xx4xx3xx2xx1=720`
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